From nobody Mon Feb 9 02:28:48 2026 Delivered-To: importer@patchew.org Received-SPF: none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1581924098070547.7172955921477; Sun, 16 Feb 2020 23:21:38 -0800 (PST) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j3ahS-0003eR-Ip; Mon, 17 Feb 2020 07:20:14 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j3ahR-0003eM-J4 for xen-devel@lists.xenproject.org; Mon, 17 Feb 2020 07:20:13 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id ef6def8e-5155-11ea-ade5-bc764e2007e4; Mon, 17 Feb 2020 07:20:12 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id CAED7AC66; Mon, 17 Feb 2020 07:20:10 +0000 (UTC) X-Inumbo-ID: ef6def8e-5155-11ea-ade5-bc764e2007e4 X-Virus-Scanned: by amavisd-new at test-mx.suse.de From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Mon, 17 Feb 2020 08:20:05 +0100 Message-Id: <20200217072006.20211-2-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200217072006.20211-1-jgross@suse.com> References: <20200217072006.20211-1-jgross@suse.com> Subject: [Xen-devel] [PATCH 1/2] xen/rcu: use rcu softirq for forcing quiescent state X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Julien Grall , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Jan Beulich MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" As rcu callbacks are processed in __do_softirq() there is no need to use the scheduling softirq for forcing quiescent state. Any other softirq would do the job and the scheduling one is the most expensive. So use the already existing rcu softirq for that purpose. For telling apart why the rcu softirq was raised add a flag for the current usage. Signed-off-by: Juergen Gross --- xen/common/rcupdate.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index 91d4ad0fd8..079ea9d8a1 100644 --- a/xen/common/rcupdate.c +++ b/xen/common/rcupdate.c @@ -89,6 +89,8 @@ struct rcu_data { /* 3) idle CPUs handling */ struct timer idle_timer; bool idle_timer_active; + + bool process_callbacks; }; =20 /* @@ -194,7 +196,7 @@ static void force_quiescent_state(struct rcu_data *rdp, struct rcu_ctrlblk *rcp) { cpumask_t cpumask; - raise_softirq(SCHEDULE_SOFTIRQ); + raise_softirq(RCU_SOFTIRQ); if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) { rdp->last_rs_qlen =3D rdp->qlen; /* @@ -202,7 +204,7 @@ static void force_quiescent_state(struct rcu_data *rdp, * rdp->cpu is the current cpu. */ cpumask_andnot(&cpumask, &rcp->cpumask, cpumask_of(rdp->cpu)); - cpumask_raise_softirq(&cpumask, SCHEDULE_SOFTIRQ); + cpumask_raise_softirq(&cpumask, RCU_SOFTIRQ); } } =20 @@ -259,7 +261,10 @@ static void rcu_do_batch(struct rcu_data *rdp) if (!rdp->donelist) rdp->donetail =3D &rdp->donelist; else + { + rdp->process_callbacks =3D true; raise_softirq(RCU_SOFTIRQ); + } } =20 /* @@ -410,7 +415,13 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk= *rcp, =20 static void rcu_process_callbacks(void) { - __rcu_process_callbacks(&rcu_ctrlblk, &this_cpu(rcu_data)); + struct rcu_data *rdp =3D &this_cpu(rcu_data); + + if ( rdp->process_callbacks ) + { + rdp->process_callbacks =3D false; + __rcu_process_callbacks(&rcu_ctrlblk, rdp); + } } =20 static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) @@ -518,6 +529,9 @@ static void rcu_idle_timer_handler(void* data) =20 void rcu_check_callbacks(int cpu) { + struct rcu_data *rdp =3D &this_cpu(rcu_data); + + rdp->process_callbacks =3D true; raise_softirq(RCU_SOFTIRQ); } =20 --=20 2.16.4 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel